Pharmaceutical composition

ABSTRACT

The present invention concerns analogues of mannose-6-phosphate for use in promoting the healing of wounds or fibrotic disorders with reduced scarring, and methods for doing same.

The present invention concerns pharmaceutical compositions for promotingthe healing of wounds or fibrotic disorders, in particular for promotingthe healing of wounds or fibrotic disorders with reduced scarring.

By "wounds or fibrotic disorders" is meant any condition which mayresult in the formation of scar tissue. In particular, this includes thehealing of skin wounds, the repair of tendon damage, the healing ofcrush injuries, the healing of eye wounds, including wounds to thecornea, the healing of central nervous system (CNS) injuries, conditionswhich result in the formation of scar tissue in the CNS, scar tissueformation resulting from strokes, and tissue adhesion, for example, as aresult of injury or surgery (this may apply to e.g. tendon healing andabdominal strictures and adhesions). Examples of fibrotic disordersinclude pulmonary fibrosis, glomerulonephritis, cirrhosis of the liver,and proliferative vitreoretinopathy.

By "reduced scarring" is meant reduced level of scarring relative to anuntreated wound or fibrotic disorder.

In particular, there is a lack of compositions for promoting the healingof wounds or fibrotic disorders with reduced scarring. Scar tissueformation, although providing mechanical strength to a healed wound, canbe unsightly and may impair the function of the tissue.

This is particularly the case in wounds which result in scar tissueformation in the CNS, the scar tissue inhibiting the reconnection ofsevered or re-growing nerve ends. so significantly affecting theirfunction.

Compositions for promoting the healing of wounds or fibrotic disordersmay also be used together with compositions for use in the treatment ofchronic wounds, for example venous ulcers, diabetic ulcers and bed sores(decubitus ulcers), especially in the elderly and wheel chair boundpatients. Such compositions may be extremely useful in patients wherewound healing is either slow or in whom the wound healing process hasnot yet started. Such compositions may be used to "kick-start" woundhealing and may then be used in combination with the compositions of thepresent invention. Hence not only may a chronic wound be healed, but itmay be healed with reduced scarring.

The activation of LTGF-β (Latent Transforming Growth Factor-β) to activeTGF-β is a critical step in the healing process. LTGF-β (which comprisesTGF-β bound to the LAP (Latency Associated Peptide) which in turn may bebound to the LTBP (LTGF-β Binding Protein)) binds to cell-surface M6P(mannose-6-phosphate) receptors via M6P-containing carbohydrates in theLAP (Purchio, M. F. et al., 1988, J. Biol. Chem., 263: 14211-14215;Dennis, P. A. and Rifkin, D. B., 1991, Proc. Natl. Acad. Sci. U.S.A.,88: 580-584; Shah, M. et al., 1992, Lancet, 339: 213-214; Shah, M. etal., 1994, J. Cell Sci., 107: 1137-1157). This binding allows theactivation of the LTGF-β a process also involving transglutaminase andplasminogen/plasmin.

Due to the binding of LTGF-β to the M6P receptor, M6P itself may play asignificant role in the healing process by competing with theM6P-containing carbohydrates in the LAP for the M6P receptor bindingsite. By increasing the quantity of M6P at a site (by "site" in thiscontext is meant a site of wounding or a fibrotic disorder), the bindingof LTGF-β to the M6P receptor may be inhibited (or at least reduced),and the levels of fibrotic and non-fibrotic TGF-β affected.

Although M6P is extremely useful, it is quickly metabolised and soprevious attempts to increase the levels of M6P at a wound site havefocused upon providing a constant supply of M6P to the wound site by theuse of slow/sustained/biocompatible non-inflammatory delivery systems.Such slow/sustained delivery systems are both costly and inconvenientand are extremely difficult to produce since it is difficult to achieveslow release from a non-inflammatory/biocompatible vehicle.

The present inventor has found that, surprisingly, analogues of M6P maybe used to promote the healing of wounds or fibrotic disorders withreduced scarring, the analogues having similar yet distinct structuresand functioning as M6P and/or inhibiting the degradation of M6P.

According to the present invention there is provided an analogue of M6Pfor use in promoting the healing of wounds or fibrotic disorders withreduced scarring.

The analogue may be a phosphonate analogue of M6P or a salt thereof.Such an analogue may, for example, be any one of the molecules of FIGS.1(a)-(f) or a salt thereof. Surprisingly, it has been found thatphosphonate analogues of M6P are capable of binding to the M6P isomerasebinding site. This allows them to competitively inhibit the binding ofM6P to the binding site and competitively inhibit M6P breakdown (i.e.M6P metabolism), therefore increasing the half-life of M6P. Even moresurprisingly, these phosphonate analogues of M6P, despite theirmolecular similarity to M6P and despite their ability to bind to the M6Pisomerase binding site, have significantly greater half-lives than M6P(i.e. are broken down at a significantly slower rate than M6P).

The analogue may have a significantly greater half-life than M6P. Theanalogue may have a half-life at least approximately 10 times that ofM6P. It may, for example, have a half-life at least approximately 100 or1000 times greater than M6P. It may be metabolised by M6P isomerase at asignificantly slower rate than M6P. The analogue may bind the M6Pisomerase receptor binding site. It may bind to the cell-surface M6Preceptor binding site.

The analogue may bind to the M6P isomerase receptor binding site. It maybind to the cell-surface M6P receptor binding site.

The analogue having a greater binding affinity than M6P for a M6Preceptor. The analogue may have a greater affinity than M6P for the M6Pisomerase receptor binding site. The analogue may have a bindingaffinity for the M6P receptor approximately 2 or 3 times that of M6P.

The analogue may be the phosphonate analogue of M6P of FIG. 1(b) or asalt thereof, having a half-life approximately 1000 times that of M6P.

The analogue may be the phosphonate analogue of M6P of FIG. 1(b) or asalt thereof, having a half-life approximately 1000 times that of M6Pand a binding affinity for the M6P isomerase receptor binding siteapproximately 3 times that of M6P.

The analogue may increase the half-life of M6P in an environmentcontaining M6P isomerase. The analogue may be for use in increasing thehalf-life of M6P in an environment containing M6P isomerase.

The analogue may be for use in the environment of the human or animalbody.

The analogue may be for use to promote the healing of wounds or fibroticdisorders with reduced scarring.

The analogue may be a n inhibitor of M6P breakdown. It may be aninhibitor of M6P metabolism. It may be an inhibitor of M6P isomerase.

The analogue may be used in conjunction with a composition for promotingthe healing of wounds or fibrotic disorders with reduced scarring. Sucha composition may comprise M6P. For example, an analogue according tothe present invention may comprise a phosphonate analogue of M6P inconjunction with M6P itself.

The analogue may be for use in conjunction with a composition forpromoting the healing of chronic wounds.

The analogue may be for use in conjunction with a pharmaceuticallyacceptable carrier, diluent or excipient.

This means that a single dose of a phosphonate analogue may have along-lasting effect upon a wound site, providing significant clinicaland therapeutic advantages. This in turn means that instead of thepresent continual supply of M6P to a wound site, a site may be given asingle dose, or several doses, of a phosphonate analogue of M6P.

By reducing the dosage of M6P to a wound site, the osmotic effect uponthe surrounding tissue at the site may be significantly reduced whencompared to the osmotic effect of a continual supply of M6P.

The analogue may be used in conjunction with a pharmaceuticallyacceptable carrier, diluent or excipient.

Hence the analogue may be functionally equivalent to M6P, yet may have asignificantly greater half-life and/or receptor binding affinity thanM6P. The analogue may not only function as M6P, but may also act toincrease the half-life and efficacy of any added or endogenous M6P byinhibiting the metabolism of M6P by, for example, M6P isomerase.

Also provided according to the present invention is a method forpromoting the healing of wounds or fibrotic disorders with reducedscarring comprising the use of an analogue of M6P according to any oneof the preceding claims.

The method may comprise administering an analogue of M6P to a site ofwounding or fibrosis.

The method may comprise the use of an analogue of M6P either immediatelybefore or immediately after wounding/onset. It may comprise the use ofan analogue of M6P within approximately 120 hours of wounding/onset,although it may be preferable to apply it within a shorter time, forexample 120, 96, 72, 48, 24 or 12 hours post-wounding/onset. By "onset"is meant the onset of a fibrotic disorder.

The efficacy of the treatment in promoting healing with reduced scarringmay be significantly enhanced by increasing M6P levels at a siteimmediately following wounding when TGF-β₁ complexed to LAP is releasedfrom degranulating platelets. The TGF-β₁ complexed to LAP is either freein the tissue fluid, bound to the fibrin clot/platelet complex, or isendocytosed into surrounding cells, e.g. fibroblasts, monocytes andmacrophages, by the M6P receptor. This degranulation and release offibrotic TGF-β₁ upon initial wounding has a number of effects whichaffect subsequent healing. In particular, the TGF-β₁ attracts monocytesand macrophages to the site, which in turn release more TGF-β₁. Byinhibiting this initial activation of TGF-β₁, which is predominantlyTGF-β₁, the ratio of fibrotic: non-fibrotic growth factors at a site maybe altered in favour of non-fibrotic growth factors and enhanced healingwith reduced scarring effected.

The method may be used in conjunction with a method for promoting thehealing of wounds or fibrotic disorders with reduced scarring.

The method may be used in conjunction with a method for promoting thehealing of chronic wounds.

Experimental work undertaken in treating wounds with non-phosphorylatedmannose and glucose resulted in retarded healing when compared withcontrols. Galactose-6-phosphate and glycerol-3-phosphate have no effectupon either wound healing or scarring.

The invention will be further apparent from the following example, whichshows by way of example only, one form of analogue of M6P which ismetabolised at a significantly slower rate and has a greater M6Preceptor binding affinity than M6P and may be used to inhibit M6Pmetabolism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows various phosphonate analogues of M6P. Figures are labelled(a)-(f) running from left to right, top to bottom;

FIG. 2 shows methods of synthesis of same; and

FIG. 3 shows (a) non-isosteric mannose phosphonate; (b)fructose-1-phosphate; and (c) maltose-1-phosphate.

EXPERIMENTAL

The wound healing and anti-scarring properties of isosteric mannosephosphonate (FIG. 1(b)) and non-isosteric mannose phosphonate (FIG. 3a),fructose-1-phosphate (FIG. 3b) and maltose-1-phosphate (FIG. 3c) weretested as described below.

Additionally, the M6P phosphonate analogue of FIG. 1(b) was prepared anda receptor binding assay performed with M6P isomerase to analyse itsbinding affinity for the M6P receptor and also to analyse its half-life.Standard methods were used to obtain the data.

Method

Adult male Sprague Dawley rats (200-250 g) were anaesthetised usingequal parts halothane, nitrous oxide and oxygen. Four linear fullthickness incisions, 1 cm in length to the depth of the panniculuscarnosus, were made on the dorsal skin, 1 cm from the midline and 5 and8 cm from the base of the skull. The wounds were left unsutured to healby secondary intention. Experimental treatments were administered byintradermal injection to the wound margins (50 μl down each woundmargin). At selected time points animals were killed by chloroformoverdose. Wounds were excised from the surrounding tissue and bisected.Half the wounds were rapidly frozen in OCT for cryosection andimmunoctyochemistry and half fixed in formaldehyde for wax embedding andhistology. Wax sections were routinely stained with haematoxylin andeosin, picrosirius red and Massons Lille trichrome, to display collagenfibre thickness, density and orientation to enable assessment of scarquality. Fructose-1-phosphate (F1P) and maltose-1-phosphate (Malt1P)were purchased from Sigma Chemical Company. A range of doses (10 mM, 20mM and 40 mM) was studied for each sugar, with PBS (phosphate bufferedsaline) as a control. Treatments were administered at the time ofwounding and each day for the following seven davs. Two animals per dosewere studied at each of the three time points (7, 40 and 80 days postwounding) for each compound. Total n=12.

Isosteric mannose phosphonate was synthesised and supplied by Dr SallyFreeman, Department of Pharmacy, University of Manchester. A range ofdoses (20 mM, 10 mM, and 10 mM+10 mM M6P) were studied, with PBS as anegative control, and 10 mM M6P and 20 mM M6P as positive controls.Treatments were administered at the time of wounding and each day forthe following two days. One animal per dose was studied at each of thetwo time points (7 and 80 days post wounding). Total n=4.

Non-isosteric mannose phosphonate was synthesised and supplied by DrSally Freeman, Department of Pharmacy, University of Manchester. Asingle concentration (20 mM) of this compound was studied, with PBS as acontrol. The time of administration varied to the previous experiments.Animals were split into three groups and treated on day 0 alone, days 0,2 and 4, or days 0 to 7 inclusive. Two animals per treatment regime werestudied at each of the three time points (3, 7 and 80 days) Total n=18.

In addition to the animal studies an ELISA-type assay using purifiedM6P/IGF II (insulin-like growth factor II) receptor was developed todetermine if these analogues of M6P bind to the M6P/IGF II receptor.

Results

Fructose-1-Phosphate and Maltose-1-Phosphate

At 7 days post wounding histological analysis showed that neither F1P orMalt1P had any effect on wound healing, when compared with PBS controls.Immunocytochemical analysis also showed that treated wounds resembledcontrols. Staining for fibronectin was consistent between treatments andcontrols as were monocyte/macrophage profiles. At 40 days post woundinghistological analysis was inconsistent, with no clear trend. At 80 dayspost wounding Malt1P appeared to improve the dermal architecture veryslightly whilst F1P appeared to reduce scarring more significantly,particularly at the highest dose studied (40 mM).

Isosteric Mannose Phosphonate

At 7 days post wounding histological analysis revealed that none of thetreated wounds appeared different to PBS controls. At 80 days postwounding the isosteric analogue appeared to improve the dermalarchitecture when compared with controls, and showed a similarimprovement in scarring as the M6P treatments.

Non-Isosteric Mannose Phosphonate

Initial histological analysis of wounds treated with 20 mM non-isostericanalogue from days 0 to 7 post wounding indicate an anti-scarringeffect, especially with the 20 mM treatment on days 0 to 7 postwounding.

The results so far obtained indicate that despite the similarity of themannose-6-phosphate analogues tested (F1P, Malt1P, and the isosteric andnon-isosteric mannose phosphonate analogues), the greater efficacy ofthe mannose phosphonate analogues may be due to their fulfilling anadditional role or having special properties with regard to theirinteractions with other molecules.

Receptor Binding Assay

Initial results from the receptor binding assay showed that F1P bindsthe M6P/IGF II receptor with similar affinity as M6P, whereas Malt1Pdoes not bind to this receptor. The results also showed that theanalogue of FIG. 1(b) had a binding affinity approximately 3 times thatof M6P for the M6P receptor binding site. Surprisingly, the results alsoshowed that despite this significantly increased binding affinity anddespite its structural similarity to M6P, the analogue had a half-lifeof approximately 1000 times that of M6P.

This suggests that other analogues of M6P, in particular otherphosphonate analogues of M6P, may have similar properties and maytherefore have great potential as inhibitors of scarring.

What is claimed is:
 1. A method for promoting the healing of a wound ora fibrotic disorder with reduced scarring comprising administering to asubject in need of such promotion an effective amount of an analogue ofmannose-6-phosphate having an anion selected from the group consistingof: ##STR1##
 2. The method for promoting the healing of a wound orfibrotic disorder according to claim 1 wherein the analogue ofmannose-6-phosphate is administered either immediately before orimmediately after wounding or onset of the fibrotic disorder.
 3. Themethod for promoting the healing of a wound or fibrotic disorderaccording to claim 1 wherein the analogue of mannose-6-phosphate isadministered within 120 hours of wounding or onset of the fibroticdisorder.
 4. A mannose-6-phosphate analog of the formula
 5. Amannose-6-phospage analog of the formula
 6. A pharmaceutical compositioncomprising the analog of claim 4 and a pharmaceutically acceptablecarrier, diluent or excipient.
 7. A pharmaceutical compositioncomprising the analog of claim 5 and a pharmaceutically acceptablecarrier, diluent or excipient.